Your Family's Germs May Move With You

THURSDAY Aug. 28, 2014, 2014 -- Your family carries its own unique population of bacteria that accompany you when you move to a new home, a new study finds.

Over the course of six weeks, seven families -- with a total of 18 people, three dogs and one cat -- swabbed their hands, feet and noses every day to collect samples of bacteria living in and on them. The participants also collected samples from household surfaces such as doorknobs, light switches, countertops and floors.

The samples underwent DNA testing to identify the different species of bacteria they contained.

"We wanted to know how much people affected the microbial community on a house's surfaces and on each other," study leader Jack Gilbert, a microbiologist at the U.S. Department of Energy's Argonne National Laboratory, said in a government news release.

The results showed that people have a major impact on the bacterial populations in their homes. For example, when three of the families moved, it took less than a day for their new homes to have the same bacteria populations as their old homes.

The researchers also found that regular physical contact between people had a strong effect. For example, in a home where there was a couple and another person, the couple shared many more bacteria. Married couples and their young children also shared many of the same bacteria.

Within homes, people's hands were most likely to have similar bacteria, while there was more variation in the types of bacteria in their noses. Homes with indoor-outdoor dogs or cats had more plant and soil bacteria, according to the study published Aug. 28 in the journal Science.

The findings suggest that by analyzing bacteria in a home, it would be possible to "predict whether a person has lived in this location, and how recently, with very good accuracy," Gilbert said.

In one case, the researchers tracked a potentially harmful strain of bacteria called Enterobacter. It first appeared on one person's hands, then the kitchen counter, and then another person's hands.

"This doesn't mean that the countertop was definitely the mode of transmission between the two humans, but it's certainly a smoking gun," Gilbert said. "It's also quite possible that we are routinely exposed to harmful bacteria -- living on us and in our environment -- but it only causes disease when our immune systems are otherwise disrupted."

The study provides new insight into the interaction between people and the bacteria that live in and on them, and play a role in their health.

"We know that certain bacteria can make it easier for mice to put on weight, for example, and that others influence brain development in young mice," Gilbert said.

"We want to know where these bacteria come from, and as people spend more and more time indoors, we wanted to map out the microbes that live in our homes and the likelihood that they will settle on us," he explained.

Learning more about bacteria is "essential for us to understand our health in the 21st century," Gilbert concluded.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about microbes.